A foam rubber molded product has been widely used, for example, for sealing parts (a weatherstrip to be attached to an automobile body, a sealing material for a door opening and closing parts of a house, etc.), general-purpose buffer materials and the like. As a rubber polymer for the foam rubber molded product, an ethylene-α-olefin-nonconjugated polyene copolymer (especially, ethylene-propylene-diene rubber (EPDM)) having excellent aging resistance and ozone resistance has mostly been used.
For a weatherstrip, sealing properties, setting resistance, lightweight properties, and the like are required. For weight saving and the like, a foam rubber is used in a weatherstrip. For further weight saving, a rubber is highly foamed to decrease the specific gravity thereof. In this case, the compression set (i.e., “setting”) is increased. Therefore, there is a problem in which the sealing performance of a product is deteriorated.
Patent Document 1 discloses a composition in which a crystallizable polyolefin resin is microdispersed in an EPDM matrix to form in the inside thereof a cell structure including an interconnected cell imparting favorable compression set and that has excellent lightweight properties (high foaming properties), and a foam.
Patent Document 2 also discloses a composition in which a crystallizable polyolefin resin is preferably microdispersed in an EPDM matrix, weight saving can be achieved, and deterioration in compression set is prevented.